Desolventizing of solvent-extracted solid particles



NOV. 18, 1952 E, H, LESLIE 2,618,560

DESOLVENTIZING OF SOLVENT-EXTRACTED SOLID PARTICLES Original Filed March 28. 1947 2 SHEETS-SHEET 1 ,0 0 3 8 d \D m m ag N H -o N 6 N DO lot!) a mm h JL 05" to U 23 01mg "'1 [L I. F 37 m i=1 H N U N m 3 ow m o v. H 03 I F.

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Nov. 18, 1952 E, H. LESLIE 2,618,560

DESOLVENTIZING OF SOLVENT-EXTRACTED SOLID PARTICLES Original Filed March 28, 1947 2 SHEETSSHEET 2 O v s. 3

,..:: :'r;" w r- LO Patented Nov. 18, 1952 nasopvsnrrzmc or SOLVENT- EXTRACTED soup rsn'rrcnns Eugene Hendrich Leslie, Ann Arbor, Mich., as-

signor to Blaw-Knox Company, Pittsburgh, Pa, a corporation of New Jersey Original application Mach 28, 1947, Serial No.

1, 1948, Serial No. 52,181

9 claims. (01. 99-2) This application is a division of my co-pending patent application Serial No. 737,915 filed March 28, 1947, now Patent No. 2,571,143, issued October 16, 1951.

My invention relates generally to the art of using solvent to extract oils and tats from divided or granular organic solid materials containing them; and in particular to the treatment of the solids after extraction to recover solvent, which treatment is generally called desolventizing. In the extraction of oils fromseeds, nuts and the like, desolventizing of the extracted residual solids is important not only to recover the solvent, but also to recover a marketable protein-containing material which is of improved quality when my method is followed and my apparatus is used. These may also be applied to extraction of animal oils and fats, as of marrow from crushed bones, fats from rendered animal materials, and in general to any similar extraction in which the solids treated are particles. My method may be adapted to suit the character of the materials to be processed, and it provides for considerable variation according to the fineness of particles. the uses for which they are intended, the nature of the solvent, and other factors.

Heretofore, it has been customary and deemed necessary to progress the solids to be desolventized o'ver heated surfaces maintained at temperatures greatly exceeding the boiling temperature of the solvent, the solids remaining in contact with the hot surface for a substantial time interval. For example, in the desolventizing of soybean fiakes and the like, it is customary to pass the flakes through a series 01' large tubes having annular concentric steam jackets maintained typically at a temperature of at least 290 F. and containing helical agitators rotating therein to move the flakes through the tubes. The time required for the passage oi the solids through such a desolventizer is commonly five to ten minutes. Even when the heating is regulated to limit the final temperature of the material discharged from the tubes, a substantial portion oi the particles is overheated for part of the treating time as a result of the prolonged contact with the hot metal surfaces. The eil'ect oi overheating, in the case oi such a material as extracted soybean flakes, is partial denaturing of the protein in the desolventized material. furthermore, the use of cumbersome equipment comprising several long jacketed cylindrical conveyors and connecting necks that are difficult to maintain, require frequent cleaning, and are high in first cost. In the use or desolventizing equip- This treatment requires,

Divided and this application October 2 ment of this conventional type, it has been common to desolventize the solids only partially in this apparatus, and to discharge into a steam deodorizer, which usually follows the desolventizer, solids still containing substantial amounts of solvent, as for example in the neighborhood of 10% by weight. In this event solvent and 'water are interchanged in the particles and much diiliculty has been experienced from the increased moisture content of the processed solids. i As the residual liquid solvent is removed from the solids, extreme fines and dust particles are freed from the mass and cause many difllculties in processing, due to their entrainment in vapors and gases and subsequent deposition on walls, tubes, paddles, etc. of vessels, condensers, and other processing apparatus. My method tends to obviate such difliculties and my apparatus is arranged to be substantially sell-cleaning, and readily accessible for further periodic cleaning.

A major object of my invention is to recover the residual solvent from solvent-extracted protein-containing organic particles at relatively low temperatures and in a very short time.

Another object is to minimize difiiculties in recovering the solvent vapors due to the dust particles therein.

Anotherobject of my invention is improved control of moisture retained by the desolventized particles; Excessive moisture at any stage is par-' ticularly objectionable due to its physical efiect on the character of the solid material, rendering it sticky or doughy rather than a free flowing and easily dispersed mass. At the same time, a substantial moisture content of controlled amount is often desirable, especially in connection with the further processing of the desolventized particles in preparing them for use as feeding supplements.

The foregoing object and other'objects and advantages will bes apparent from the following description of my method and apparatus.

According to my method, the extracted solid particles are passed continuously through a. treating zone in contact with vapors evolved from the particles, the vapors being continuously withdrawn from the zone, superheated, and returned thereto, and a portion of the vapors from which the superheat has been substantially used is continuously removed, condensed, and recovered in liquid form for reuse in the extraction of more solids. The flow of vapor with respect to the solid particles may be co-current or countercurrent, there being certain advantages character istic of each flow; and a preferred practice 01' m method provides for both types oi flow in'nove and advantageous manner. Heating of the vapors is regulated to maintain a temperature of solids delivered from the zone onlyslightly higher than the boiling point of the solvent. These vapors. thus having only sufllcient sensible heat to supply the latent heat to evaporate the solvent contained in the solids, cool quickly in the contacting zone without raising the temperature of the solid par ticles appreciably.

Ordinarily, the vapors recirculated consist chiefly of solvent vapor and water vapor, the latter being present because it is usually a component of the solids prior to solvent extraction. The vapor pressure of the water in the solids. is. however, appreciably depressed by its presence in the solid phase. This does not appear to be true of the solvent, at least to a noticeable extent. The result is that the vapor removed from the solids is not of the azeotropic composition which it would have in the absence of the solid phase; but the evaporation nevertheless does occur at a temperature somewhat lower than the boiling point of pure solvent. The composition of the atmosphere in the treating zone of my method may be modifled by addition of other vapors or gases to those evolved from the solids. which addition may be desired for various reasons, as for example, to lower the temperature of effective evaporation or to control the residual moisture content of the desolventized product. The former may be eflected by addition of an inert gas, the latter by addition of steam.

My apparatus which is specifically claimed in outlet eflects a rapid drop in vapor temperature which effectively insures against subsequent overheating of the particles. At the same time, advantage is taken of the greatest temperature drop of a substantial portion of the vapor, and the net evolved vapor is delivered at approximately saturation temperature, providing excellent thermal economy of operation.

One form of my apparatus I prefer for desolventizing solvent extracted vegetable materials comprising relatively coarse solid particles high in protein of which flaked soybeans is typical. These particles are rather fragile flakes, containing only a limited amount of dust. It is essential that they be gently handled to preserve their coarse structure, and to avoid excessive forma- "-t ion of dust and flne particles. It is also beneparatus does, eflect intimate mingling of the solid particles 'with the circulating heated vapor.

As was previously mentioned, the continuous contacting of particles with vapor may be counter-current or co-current or a combination of the two. An advantage of co-current flow is that the hottest vapor contacts the particles containing the most solvent, which provides the highest degree of protection against overheating of the particles. Advantages of counter-current flow reside in the greater vapor temperature drop available for heat exchange, and in the cleansing action of the liquid-wetted particles on the dustladen vapors. In a preferred practice of my method and as provided particularly by a preferred embodiment of my apparatus, the superheated vapors are introduced at an intermediate point along the path of the particles, and passed incircuits in both directions, in substantially equal parts; and the net evolved vapor is removed from the solids inlet point of the desolventizer. By this means, the vapor passes through solvent wetted particles as it flows towards the outlet. and a substantial amount of entrained dust is removed thereby. The particles being treated contain substantially hall of their original liquid solvent when they arrive at the hottest vapor zone, and the probability that any dry particles arrive there is extremely remote, and co-current flow thereafter towar t 5011615 iicial to avoid heating these flakes excessively, to prevent undesired denaturing of the protein and other possible adverse chemical and physical changes. As this embodiment is an excellent illustration of one important application of my invention, I will describe it rather fully as applied in the art of extracting the oil from soybeans with hexane.

The beans are prepared for extraction in the usual manner by cracking the beans and conditioning the cracked beans as to temperature and water content and flaking the conditioned pieces between rolls. The flakes are then contacted with solvent in any desired manner. A suitable and preferred extractor is the basket-type in which the material is carried through a flxed circuit in baskets having perforated bottoms, the solvent deluging the baskets in. transit and continuously draining through the flakes. After final drainage at the end of the circuit the extracted flakes are discharged from the baskets into an enclosed conveyor, which moves the solvent-wet flakes to the inlet of the desolventizer. The conveyor casing provides a fluid conduit for solvent vapor which is maintained under slight suction by the fans presently to be mentioned. The desolventizer is a cylindrical vessel lying generally horizontally and containing a slowly rotating agitator which moves the flakes longitudinally and causes a, gentle cascade of the particles as they pass through a heating zone in the vessel in transit towards the opposite or discharge end of the vessel. A fan withdraws solvent vapor from the desolventizer and circulates it through a heater and back again to the desolventizer in the zone where material is cascaded through the vapors by the agitator. The circulating superheated vapor drives oil more solvent from the material, this evolution occurring chiefly in the region of the apparatus close to the hot vapor inlet, at which point a high-temperature zone prevails in the vapor, the temperature in the remainder of the apparatus being substantially lower. Heating of the vapors is controlled to maintain a substantially constant temperature at the solids discharge outlet, preferably slightly above the boiling point of the solvent. A thermometer or temperature controller is provided near the solids outlet for this purpose. The vapor evaporated from the flakes is withdrawn through a thermally jacketed dust separator and fan to a condenser. The material is transferred from the desolventizer by means of a vane feeder or rotary vane lock for further treatment to a deodorizer, which is a horizontal cylindrical vessel having treated walls and a rotating agitator, in which the material is contacted with steam. Here the last trace of solvent is removed, along with undesirable volatile components of the flakes adversely affecting their aroma and taste. The completely desolventized and deodorized material is discharged through a second vane feeder to a conveyor which removes it to a further treating apparatus or for other disposal, and the steam and solvent vapors are cleaned and condensed, conveniently by the same dust separator, fan and condenser provided for the desolventizer vapors. It has been customary to waste fines separated from solvent vapor, but in my method they may be recovered, preferably by returning them to the particle stream near the solids discharge end of the deodorizer. where the vapor velocity is low and the path to the solids outlet is relatively short.

Concerning the factors which are important in the carrying out of my method, the temperature to which the circulating atmosphere is heated in the vapor heater ma be any conveniently attainable by use of heating steam; the amount of vapor recirculated must be suflicient to afford, as sensible heat, enough heat to evaporate the solvent from the flakes; the velocity of vapor in contact with the particles should be low. preferably below 120 feet per minute, and the vapor velocity in the heater should be relatively high to favor rapid heat exchange. Conveniently. the heater is a heat interchanger supplied with steam commonly available in extraction plants in the neighborhood of 100 lbs. per sq. inch, which permits heating the recirculatin vapors to about 300 F. Commercial hexane is an excellent solvent, quite generally used, having a boiling range between 140 F. and 160 F., a latent heat of vaporization at 150 F. of about 144 B. t. u. per 1b., and an average specific heat of vapor between 300 F. and 150 F. of about 0.45 B. t. u. per lb. per T. It consists principally of pure hexane boiling at approximately 150 F. Excluding the effects of other components in the atmosphere such as steam and inert gases, and assuming the vapors are superheated to about 300 F., about three pounds of hexane vapor should be circulated through the fan and heater for each pound of liquid solvent evaporated. This rate of circulation may be varied within practical limits, and between two to four pounds of vapor circulated to the superheater per pound of vapor evaporated is a preferred range. Another factor, however, is of the greatest importance, namely maintaining a maximum flake temperature at or below 165 F. I have discovered that by desolventizing protein-containing solvent extracted particles with heat while maintainin a flake temperature below about 165 F., a much improved product is obtained which heretofore could not be produced commercially. This product is lighter in color and yields more protein on protein extraction than does the same original material desolventized according to prevailing practice.

The limitation to 120 feet per minute velocity for vapor flowing in contact with the particles is particularly important to avoid blow-back of particles in counter-current treatment, and in both co-current and counter-current contacting, to prevent excessive entrainment of particles in the vapors circulated through the heater; but higher velocities are contemplated in certain instances of comurrent treatment where centrifugal separation of vapor and particles is interposed between the contacting and heating steps, and my method and apparatus are not limited in all embodiments to any particular maximum vapor velocity.

In connection with the maximum flake tem perature. it should be noted that while various known expedients may be employed to limit or lower the temperature of the flakes during the desolventizing process, such as employing unusually low-boiling solvents for extraction, desolventizing under vacuum, and the like, such expedients are undesirable for the most part, for reasons obvious to those skilled in the art; and my method provides inherently a protection against flake overheating which renders such expedients unnecessary. As the flakes are cascaded through the superheated vapors delivered from the heater, their maximum temperature is limited to the solvent boiling point so long as evaporation proceeds, and may be somewhat lower due either to concurrent evaporation of water from the flakes or to the presence of some inert gas. A very large surface of contact is presented by the particles and the vapors are quickly cooled to a temperature approaching the saturation temperature, unless they have been excessively superheated, so that flakes as they are desolventized pass quickly into a low temperature zone. Hence a simple control of heat supplied to the vapor heater, regulating the supply to be just sufficient for evaporating the solvent, or but slightly in excess of this requirement, effectively determines the maximum temperatures to which the flakes are heated in my apparatus and according to my method; and I preferably control the admission of steam to this heater in accordance with the temperature of the outgoing meal, so as to maintain this temperature at or below F. In case a solvent for extraction is selected which has higher boiling point than hexane, as for example commercial heptane having a boiling range of 177 F. to 233 F. or in case a material temperature lower than or approaching the boiling temperature of hexane or other solvent is desired as the control level, an inert gas such as nitrogen or carbon dioxide may be introduced into the desolventizer to reduce the partial pressure of the solvent and effect a saturation temperature in the evaporating zone lower than the solvent boiling point and somewhat lower than the control temperature selected for the maximum temperature of the flakes bein desolventized.

Steam is an excellent direct heating medium but when it is used as the principal vapor contacting the solids containing solvent of lower boiling point than water, rapid exchange of liquid water for liquid solvent occurs in the solids which increases the moisture content. The physical characteristics of the solids may be radically aflooted by this, there bein locally produced doughy masses, which causes severe material handling difllculties when steam is used for desolventizing, even when the total available heat is sufflcient to, and eventually does, subsequently reduce the moisture content of the material to a lower value. In my process, some steam can advantageously be admitted to the desolventizer to modify the proportional atmosphere of solvent and water vapors, which in equilibrium with the material establishes or regulates the moisture content at some desired determinable value; or the use of added steam can be deferred until the deodorizln step, when the solvent content of the solids or flakes is low and the exchange of water for solvent does not result in excessively moistening the particles. I prefer in any case to reduce the solvent content of the solids to 4% or less before treating the flakes in the deodorizer wh r steam is the principal atmosphere. The deodorizer is jacketed so as to have heated inside walls. providing an extensive heating surface or heat source other than the steam inside the deodorizer. so that the system is flexible and can be used to decrease or increase the moisture content of the flakes as desired. Dry steam is continously passed through the deodorizer in contact with the flakes, which effectively removes all residual solvent and volatile odoriferous components. The vapor velocity in the deodorizer is quite low and entrainment of dust in the vapors is but slight.

Vapors are withdrawn from the desolventizer and deodorizer, combined, and passed through a heated dust separator, preferably of the centrifugal type, under suction of a fan which thence delivers them to suitable condensers in which solvent and water are liquified and removed. Any vapors not condensed in this manner are delivered to a vent condenser, under suction from a fan, which cools the gases passing through it to a temperature sufficiently low to discharge substantially solvent-free non-condensible gases to the atmosphere. The fan does suflicient work on the gases and vapors to overcome the friction through the condensers and dust separator and to maintain a slight vacuum on the extractor. so that proper direction of flow of vapors and gases is insured throughout the system.

Condensate, consisting of solvent and water, drains to a decanter in which these liquids are separated. Solvent is returned to the extractor and the water is discharged to a sewer, usually after being boiled to render it solvent free.

In the desolventizer described above, mechanical means is employed to gently disperse the particles in the heated atmosphere and to progress them through the treating zone. My method and apparatus, however, are not necessarily limited to the use of this expedient. Nor are they limited only to processes in which the particles are subsequently deodorized with steam. For example, it is within the contemplation of my method to arrange the desolventizer vertically and pass the solids therethrough from the top to the bottom, under the action of gravity. Vapors evolved from the particles in this case are removed at or near the top of the vertical desolventizer, passed through the heater, and returned at or near the bottom to rise through the particles countercurrent to their descent. Such apparatus may be of large volume. and the flow of vapor and particles may be adjusted to eil'ect desolventizing as the solids fall freely through the vapor atmosphere, or the solids may be retarded to form a slowly flowing bed or mass through which the superheated vapor is passed. Suitable provision is made, of course, to separate solids particles from vapors diverted to th heater and the net evaporated vapors discharged to the condensers. The particles may or may not be deodorized after leaving the bottom of the apparatus, depending, of course, on whether such subsequent treatment is desired.

My method will be more perfectly understood in the following description with reference to the accompanying drawings in which Fig. 1 shows diagrammatically one example of my complete desolventizing and deodorizing system. certain apparatus being indicated in elevation and partially in section;

Fig. 2 shows a longitudinal sectional elevation of the desolventizer in greater detail. on the line II-II of Fig. 1; and

Fig. 8 shows diagrammatically another example of my desolventizing system.

Referring first to Fig. l, drained extracted flakes to be desolventized are delivered continuously to my treating system from th enclosure of a suitable extractor (not shown) through conveyor casings I, two of which are indicated side by side and may conveniently be screw conveyors. Desolventized flakes finally leaves my system through conveyor 2, which may be of any convenient type. Recovered solvent is delivered by the pump In and waste liquor is discharged to the sewer 4. These elements generally define the terminal points of my system.

Th discharge ends of the casings of feed screws I enter the desolventizer i0 through a lateral wall in a dome ll near one end, being sealed therein to prevent leakage of vapor. The desolventizer I has an insulated cylindrical casing l2, extending generally horizontally and containing a rotor (3 which sweeps the walls of the casing and is arranged to progress the particles towards the outlet nozzle IS. A thermometer or other temperature responsive device I4 is provided near this outlet nozzle. Vapor is withdrawn from intermediate steam-jacketed domes I6 and i1 through steam-jacketed ducts lie and l'la to the suction inlet of a fan It. which discharges through a flaring transition passage l9 and the vertical tubes of the heater 20 back into the casing It. The tubes 20a of the heater extend between tube sheets 20b at opposite ends of the shell Mic. The shell is supplied with heating steam, which surrounds the tubes. It will be apparent that the superheated vapor from the heater 2!) divides and passes in opposite directions to the domes I6 and I1, providing two circuits for the vapor, one countercurrent and the other co-current with the particles. This is a preferred arrangement, particularly for desolventizers of the larger sizes and capacity; but in smaller sizes, the dome l1 and conduit Ha may be omitted, eliminating the co-current circuit. In the single counter-current circuit arrangement (dome I1 and conduit lla being omitted) the duct Illa. will be substantially larger as the entire recirculating flow passes through it. Where, however, two domes l6 and I1 delivering vapor to the same heater III are used, the flow through ducts lid and Ila is preferably made unequal, so as to effect substantially equal vapor flow within the desolventizer from the heater outlet in opposite directions. Where hexane is the solvent, this requires maintaining the flow through duct Ila approximately twice that in duct lBa; and Fig. 1 shows ducts 16a of smaller size than llc for this reason. Flakes from the desolventizer outlet I5 are transferred through vane feeder 2| and duct 22 to one end of a lower vessel 23 generally described as a deodorizer. This consists of a generally horizontal steam-jacketed cylindrical casing 2| containing a rotor 25 which sweeps the inside wall to pass the material towards the outlet nozzle 18, and having a steam inlet 21, vapor outlet dome 28, and dust return inlet 29. From the outlet nozzle 28 the particles are transferred through a second vane feeder II to the discharge conveyor 2. 1

A vapor outlet-dome II is provided in the top of the desolventizer III at the solids inlet end, from which the evaporated solvent and water evolved by heating the flakes is removed. These and the vapors from dome 28 of the deodorizer are withdrawn through stem jacketed ducts 30 and 3| respectively and passed to the jacketed centrifugal dust separator 32. Solids removed from vapors in the dust separators are returned to the deodorizer by a vane feeder 2Ic. The dust separator 32 is connected by jacketed duct 33 to the suction side of a fan 34, which fan discharges to a condenser inlet duct 35. The net delivery of release vapor from duct 35 enters a condenser 33. Non-condensibles and a slight trace of lower-boiling solvent pass from condenser 36 to a supplementary vent condenser 31 which is exhausted and maintained under low pressure by the fan 33. Other apparatus in the extraction plant is also vented through condenser 31, pipe branch 39 indicating a conduit from such sources of vapor.

It will be understood that all vapor ducts and conduits, domes I I, I6, and ll of the desolventizer, the dust collector, and in general apparatus through which dust-laden vapors pass, are preferably steam-jacketed to prevent solvent condensation. The dust carried by the vapors accumulates at wet spots, forming obstructions which interfere with operation of the appparatus. Jacketing or other heating means applied to walls in contact with the vapors effectively cures this difficulty. The use of jacketing is well known for this purpose and is mentioned here only as a precaution which is significant in the successful application of my method and use of my apparatus.

Liquid recovered in the condensers 36 and 31 drains through pipes 40, 4|, and 42 to a decanter 43. This is a tank divided' into two compartments M and 45 by separating bulkhead or weir 46. Pipe 42 discharges into compartment 44, in which the water and other heavy substances settle to the bottom and are withdrawn through overflow 41 to the sewer 4. Means for boiling the waste water are not shown for simplicity of the drawing, but it is understood that such means, well known to the art, are ordinarily provided. Solvent floats on top of the water and overflows into chamber 45, from which it is withdrawn through pipe 48 and pump 3. This specific portion of my system is an illustration of the step of separating recovered solvent from water and may be followed exactly where the solvent is lighter than, and immiscible with water. Where the solvent is miscible with water, or heavier than water, suitable modifications well known in the art may be made to my system to provide this separation. The particular illustration is selected because most oil and fat extraction with solvent uses solvents lighter than and immiscible with water.

Returning now again to the desolventizing vessel, it will be observed that two vapor removal domes I6 and H are shown, spaced longitudinally on the top of the casing on opposite sides of the vapor heater 20, the center of which, however, is offset from the centers of the domes. The ducts lid and I'Ia are made as short as possible to form a continuous passage which connects, near its center, directly to the suction inlet of the fan Ill. The fan rotor and heater 20 have their centers in the same vertical plane, the fan being closely adjacent to the heater 20 and inlet transition l3, discharging thereinto as directly as possible. This arrangement is extremely compact and permits ducts of the shortest possible length, which is important in conserving heat and preventing chilled spots in the ducts whichpausc deposition of dust particles and obstruction of the passages. Furthermore, the heated vapors divide in the desolventizer and flow therethrough in opposite directions, with half the velocity that is required where the flow is unidirectional, and providing the additional advantages of countercurrent and co-current contacting in sequence previously pointed out. At the same time, vapors flow through the heating tubes 20a at relatively high velocity, a condition favoring a high rate of heat transfer and permitting apparatus of economical size.

A removable screen tray I9a is provided at the r lower end of the transition cone I9. The screen effectively catches any large agglomerations of dust particles which may have been formed at cool spots in the ducts and passed through the fan, preventing their falling on the tube sheets and fouling the tubes. The ducts Iia and Ila. are preferably steam-jacketed to prevent such cool spots. The screen may be taken out periodically for cleaning. It is best shown in Fig. 2.

The rotor I3 which turns within the desolventizer is arranged to pass the solid particles from the inlet end towards the discharge end, and, in the zone under the outlet from the heater 20, to lift and cascade the particles through the circulating heated atmosphere. The rotor has stub shafts I 3a and I3b journalled in the opposide ends of the desolventizer, the shaft I3a being driven through transmission 49 by the motor 50. Affixed to the inside ends of shafts I3a and I3b are torque discs I3c having a diameter slightly less than the inside diameter of the desolventizer casing l2. Between the discs I3c at their circumference, extend helical ribbons I3d and longitudinal bars I3e. The ribbons, as they rotate, pass the solid particles towards the desolventizer outlet. The bars I3c have fiat rectangular section generally perpendicular to radii through the axis of the rotor so as to tie together successive turns of the helical ribbon throughout the length of the rotor, stiffening it mechanically; and in addition, in the zone between the vapor domes l1 and IS, the bars I3e have flanges I3 extending radially between adjacent turns of the helix providing lifting paddles which scoop up the solid particles from the bottom of the desolventizer, and as they turn drop the particles causing them to fall through the vapor. This embodiment of my invention thus includes means for progressing the particles longitudinally, exemplified in this instance by the helical ribbons of the rotor, and means for dispersing the solid particles in the heated vapor atmosphere.

Three principal zones are characteristic of the foregoing example of my desolventizer; a heating zone between the vapor domes I6 and H in which the highest vapor velocityipreferably about feet per minute or less) is maintained and the flakes are cascaded through the moving vapors in intimate contact therewith; a settling zone from the outlet dome I I extending longitudinally to the heating zone, through which outgoing vapors only pass (in the case of hexane at a velocity about one-half of that of the heating vapors, or less than 60 feet per minute) countercurrent to solvent-wetted particles which de-superheat the vapors and catch and remove a portion of the entrained dust; and a settling zone disposed vertically within the dome II itself, out of contact with particles. This arrangement is even more effective when only one vapor dome I8.is provided instead of two, since the ratio of vapor velocities in the heating and settling zones respectively is then greatly increased, being in case of hexane vapors, substantially four to one 11 instead of two to one. It will be apparent that this construction provides for minimum entrainment of dust by the solvent vapors. and further for appreciable elimination of much of the dust entrained before the vapors are discharged from the desolventizer.

The vane feeders ll which control the admittance of flakes to the deodorizer 23 and discharge of flakes therefrom are of well known They each consist of a horizontally cylindrical casing Ila closed at the ends and having inlet and outlet passages at the top and the bottom. Within the casing turns a vaned rotor I lo, the vanes dividing it' into radial segments. The rotor does not flt tightly in the casing. but baiiies the passage for patricles to obstruct inter-mingling and dispersion of the diverse atmosphere on opposite sides of the rotor. Undesired net flow of vapors and gases through the feeder is prevented or controlled by balancins pressures in the various units of the apparatus. It is generally preferable that the pressures be substantially-equalized across the feeder at the desolventizer inlet and outlet. The rotor 2 lb may be driven at suitable speed by any convenient means, as by an electrical motor and transmission indicated at it.

Particles leaving the desolventizer i ordinarily still contains a trace of residual solvent which is finally removed by steam treatment in the deodorizer 23. This vessel is a generally horizontal cylinder having a double-walled casing 2 which provides a Jacket for heating steam, to impart heat to the particles as well as to avoid cool spots favorable to deposition of solids entrained in the vapor atmosphere, and thus prevent undesired condensation of water vapor. Saturated or slightly superheated process steam is admitted at steam inlet 21 and withdrawn at outlet 28. The rotor 25 is generally similar to "the rotor it of the desolventizer previously described, being constructed with stub shafts 25a and 25b, torque discs Iic, helical conveying ribbon 25d, and bars 25c. Shafts 25a. and 25b are journalled to turn in bearings in the heads of the desolventizer casing it and shaft 25:: is driven through a transmission 52 by motor 53. The solids inlet duct 2! and steam inlet 21 are at opposite ends of the deordorizer, providing countercurrent flow of vapor and flakes between the outlets 2B and 28 for flakes and vapor respectively.

Fig. 3 illustrates a modified form of my apparatus with the desolventizer arranged vertically, in which the solids are progressed principally by gravity. The particles to be desolventized are delivered by a screw conveyor I through nozzle Bl! of the desolventizing vessel 54 at the top thereof. This vessel is preferably in form of a truncated cone, being circular in section and slightly larger at the bottom than the top, to prevent hanging up of the particles on the lateral surfaces. A vertical shaft 5! extends axially of the vessel, being driven to rotate at slow speed by the geared motor 58. Mounted on the shaft are radial arms 51 and 58. which gently agitate the solid contents of the vessel. The lowermost arms Bl sweep the particles into the discharge nozzle 58, whence they are passed by vane feeder II to discharge conveyor 2. A thermometer ill may be conveniently located in the nozzle u.

A manifold 8i girdles the bottom of the vessel 54, having a plurality of vapor openings 62 for discharge of superheated vapor. An outlet 63 for recovered solvent vapor is provided in the top of the vessel. A second outlet 64 is connected by 12 a duct 61 to the suction side of a fan It. The vessel preferably is not filled completely with solids. but a substantial vapor space is left below the opening it for gravity separation of entrained solids from the vapor. The fan ll blows the vapor at a controlled rate through transition cone l9, heater 2B, funnel 65, and duct 66 to the manifold I. The net vapor evolved from outlet BI is delivered to condensing and decanting apparatus, not shown in Fig. 3, but which may be substantially the same as condensers II and 31 and decanter ll of Fig. 1. Parts numbered with the same reference numerals shown on Fig. 1 and described in connection therewith, are of essentially the same construction in this example, illustrated by Fig. 3, and further description of them need not here be made. If the solids to be processed are fine or dusty in character, a dust collector such as I: previously described may be interposed between the vapor outlet 61 and the cong ensilng apparatus, substantially as shown in superheated vapors entering through the openings 62 rise through the agitated mass of particles and rapidly become saturated with evaporated solvent and water, cooling rapidly to saturation temperature. Mild agitation of the solids by the paddles 94 tends to prevent channeling and to insure thorough desolventizing of the particles.

Although I have illustrated and described but two embodiments and a preferred practice of my invention, it will be recognized that changes in details of construction disclosed and variations in the application of my method may be made without departing from the spirit of my invention or the scope of the appended claims.

I claim:

1. The method of preparing a protein rich vegetable feed supplement comprising extracting oils and fats from prepared natural vegetable particles by means of a volatile solvent, evaporating residual solvent from the particles by contact with a superheated vapor atmosphere consisting principally of vapors evolved from the particles, and blending added water vapor with said atmosphere to establish a water vapor pressure in the atmosphere substantially in equilibrium with the particles at a desired moisture content, thereby producing a substantially solvent free product, containing moisture in controlled amount.

2. The method of desolventizing solvent extracted particles comprising progressing the particles in sequence through vapor settling and vapor contacting zones, maintaining a circulation of superheated vapor in said contacting zone. dividing the said superheating vapor in said contacting zone into two oppositely flowing portions which move counter-currently and eo-currently with said particles, and removing evolved vapor from said settling zone.

3. The method according to claim 2 characterized by maintaining an average vapor velocity in said contacting zone of less than feet per minute and an average velocity in said settling zone of approximately one-half of the velocity in said riolntacting zone.

the continuous desolventizing of solventwet extracted organic particles by heating the particles directly with solvent vapor. the improvement comprising maintaining a substantially uniform movement of extracted particles in dispersed condition. passing vapors to be condensed and recovered in countercurrent contact with the flow of particles where they are solventwet to desuperheat and scrub the vapors of entrained solid dust, recirculating in a closed circuit a stream of vapors at a substantially constant rate of flow greater than the rate of flow of the aforesaid evolved vapors to be condensed, superheating the said stream of vapors in said circuit out of contact with the particles, and contacting the flow of dispersed particles with said superheated vapors in another portion of said circuit, the said last mentioned contacting being efl'ected after the particles have been contacted with the first mentioned vapors.

5. In a continuous method of desolventizing solvent-extracted particles comprising progressing the particles through a settling zone and through a contacting zone, admitting superheated vapor into said contacting zone to contact said particles and evolve additional vapors therefrom, maintaining the volume of said superheated vapors so admitted greater than the volume of the vapors evolved, and withdrawing said vapors from said settling zone, generally in the quantity so evolved, said zones being substantially at atmospheric pressure, whereby the velocity of said evolved vapors passing through said settling zone is less than the velocity of said vapors passing through said contacting zone.

6. In a method of removing solvent from solvent-extracted organic particles, the steps comprising, continuously moving the particles through an enclosed zone, continuously circulating superheated vapors of such solvent through said zone to vaporize said solvent in said particles, continuously reheating that portion of said vapors in excess of the quantity formed by evaporation in said zone and reintroducing that portion into said zone, and continuously controlling the extent of said reheating by the temperature of the particles leaving said zone to maintain the maximum temperature of said particles at not substantially in excess of the boiling point temperature of said solvent at the vapor pressure of said solvent existing in said zone.

7. In a method of removing solvent from solvent-extracted organic particles, the steps comprising, continuously moving the particles through an enclosed zone having heating and settling portions, continuously circulating superheated vapors of such solvent through the heating portion of said zone to vaporize said solvent in said particles, continuously withdrawing vapors from said zone through the settling portion thereof in a quantity generally equal to the quantity of vapors formed by evaporation in said zone, and continuously reheating the vapors not so withdrawn and reintroducing them into said zone.

8. In a method of removing solvent from so]- vent-extracted organic particles, the steps comprising. continuously moving the particles through an enclosed zone having heating and settling portions, continuously circulating superheated vapors of such solvent through the heating portion of said zone to vaporize said solvent in said particles, continuously withdrawing vapors from said zone through the settling portion thereof in a-v quantity generally equal to the quantity of vapors formed by evaporation in said zone, and continuously reheating that portion of said vapors not so withdrawn and reintroducing them into said zone at an intermediate point in the heating portion thereof.

9. In a method of removing residual solvent from organic particles extracted with lower boiling normally liquid hydrocarbon solvents such as commercial hexane, the steps comprising, continuously moving the particles through an enclosed zone, continuously circulating superheated vapors of said solvent through said zone to vaporize said solid in said particles, continuously withdrawing vapors from one portion of said zone in a quantity generally equal to the quantity of vapors formed by vapors in said zone, continuously withdrawing the balance of vapors in said zone therefrom at another portion of said zone, said balance of said vapors being generally from about two times to about four times the volume of vapors formed by evaporation in said zone, continuously reheating said balance of vapors before reintroducing them into said zone. controlling the extent of said reheating by the temperature of the particles leaving said zone to maintain the maximum temperature thereof below about 165 F., and maintaining substantially atmospheric pressure in said zone.

EUGENE HENDRICH LESLIE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 245,274 Byerley Aug. 9, 1881 309.485 Muzinger Dec. 16, 1884 705,787 Pratt July 29, 1902 747,267 Swenson Dec. 15, 1903 918,335 Lain Apr. 13, 1909 1,261,005 Barstow et al. Apr. 2, 1918 1,515,596 Harris Nov. 18, 1924 1,820,986 Peebles Sept. 1, 1931 1,934,677 Ash Nov. 14, 1933 2,119,261 Andrews May 31, 1938 2,152,665 Rosenthal Apr. 4, 1939 2,254,867 Bonotto Sept. 2, 1941 2,320,970 Lansing Jun 1, 1943 2,334,015 Levine et al. Nov. 9, 1943 2,377,135 Dinley et a1 May 29, 1945 2,467,435 Langhurst Apr. 19, 1949 2,491,060 Robinson Dec. 13. 1949 Certificate of Correction Patented November 18, 1952 Patent No. 2,618,560

EUGENE HENDRICH LESLIE It is hereby certified that it appears that mistakes have been made id the above numbered patent and a showing has been made that such mistakes occurred in good faith and were not the fault of the Patent Ofiice, said mistakes requiring correction as follows:

Column 8, line 10, for 3n read 3; column 14, line 21, for solid read solvent; line 24, for vapors, second occurrence, read evaporation.

The said patent should be read as though corrected as specified.

Signed and sealed this 24th day of March, A. D. 1953.

THOMAS F. MURPHY,

Assistant Commissioner of Patents.

Certificate of Correction Patent N0. 2,618,560 November 18, 1952 EUGENE HENDRICH LESLIE It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 2, line 40, for bes read be; column 8, line 73, for stem read steam; column 9, line 1, for separators read separator; line 6, for release read released; column 10, line 26, for the syllable side read site; column 11 line 16, for patricles read particles; line 49, for deordorizer res. deodorizer; column 13, line 23, after zone strike out the comma; and that the said Letters Patent should be read as corrected above, so that the same may conform to the record of the case in the Patent Oflice.

Signed and sealed this 24th day of March, A. D. 1958.

[seat] THOMAS F. MURPHY,

Assistant Commissioner of Patents.

qekioimambb Certificate of Correction Patent No. 2,618,660 November 18, 1952 EUGENE HENDRICH LESLIE It is hereby certified that error appears in the tinted specification of the above numbered patent requiring correction as ollom:

Column 2, line 40, for hes read he; column 8,'line 78, for stem read steam; column 9 line 1, for separators rea'd separator; line6, for release read released; coiumn 10, line 26, for the syllable aide rend site; column 11 line 16, for patricles read particles; line 49, for deordorizer rea deodorizer; column 13, line 23, after zone 'strike out the comma;

' and that the said Letters Patent should be read as corrected above, so that the same may conform to the reeord of the case in the Patent Ofiicc.

Signed and sealed this 24th day of March, A. D. 1953.

THOMAS F. MURPHY,

Assistant Gorhmiuioner of Patents. 

1. THE METHOD OF PREPARING A PROTEIN RICH VEGETABLE FEED SUPPLEMENT COMPRISING EXTRACTING OILS AND FATS FROM PREPARED NATURAL VEGETABLE PARTICLES BY MEANS OF A VOLATILE SOLVENT, EVAPORATING RESIDUAL SOLVENT FROM THE PARTICLES BY CONTACT WITH A SUPERHEATED VAPOR EVOLVED FROM THE CONSISTING PRINCIPALLY OF VAPORS EVOLVED FROM THE PARTICLES, AND BLENDING ADDED WATER VAPOR WITH SAID ATMOSPHERE TO ESTABLISH A WATER VAPOR PRESSURE IN THE ATMOSPHERE SUBSTANTIALLY IN EQUILIBRIUM WITH THE PARTICLES AT A DESIRED MOISTURE CONTENT, THEREBY PRODUCING A SUBSTANTIALLY SOLVENT FREE PRODUCT, CONTAINING MOISTURE IN CONTROLLED AMOUNT. 